Biomedical subjects

K R Laws

Publications and source records attributed to K R Laws.

3 recordsLinked to original sources

PubMed1995

Object recognition without knowledge of object orientation.

Several theories have been proposed to explain our ability to recognise objects from a number of viewpoints. Orientation-dependent accounts emphasize the position of the object relative to the viewer, while orientation-independent accounts (e.g. Marr) rely on descriptions of an object's component parts relative to its principal axis of elongation. An opportunity to compare the merit of these theories has arisen in a patient (L.G.) who had a rare neuropsychological sign in which knowledge of the canonical upright of object drawings was profoundly disrupted. Such orientation errors were evident in her drawings from memory and to copy, and in an orientation-matching task. In a critical experiment she showed a deficit in providing the canonical upright of individual object drawings that was independent of any difficulty in object recognition. The implications of these data for theories of object recognition are discussed.

Adult↗

PubMedDate not supplied

Probing sensory and associative semantics for animals and objects in normal subjects.

Neuropsychological studies of patients with "category-specific" semantic memory disorders have fuelled a debate concerning the organisation of knowledge. In particular it has been suggested that the reported double dissociation between knowledge of animals and living things on the one hand, and objects on the other, reflects a more fundamental division of semantic representation into functional-associative and sensory-visual domains. The present study attempted to investigate whether there were systematic differences along these dimensions in normal subjects using a sentence-verification technique. It was found that response times were significantly longer for verification of statements concerning the sensory attributes of objects than for statements about their associative attributes. In the case of animals, there were no differences in response latency to associative or sensory statements. In the light of this previously unreported fractionation within verbal semantics, the possible consequences for models of semantic memory are discussed.

Adult↗

PubMedDate not supplied

Naming without knowing and appearance without associations: evidence for constructive processes in semantic memory?

This study describes a patient (SE) with temporal lobe injury resulting from Herpes Simplex Encephalitis, who displayed a previously unreported impairment in which his knowledge of associative and functional attributes of animals was disproportionately impaired by comparison with his knowledge of their sensory attributes (including their visual properties and characteristic sounds). His knowledge of man-made objects was preserved. A striking aspect of the present case was that the patient remained able to name many animals from their pictures, despite making gross errors in generating associative information about these same animals. This suggests that a semantic representation incorporating stored sensory knowledge may be sufficient for naming (at least for biological categories) and associative information may be unnecessary. Semantic knowledge may normally incorporate more information than is necessary for identification. SE's errors were found to be confabulatory and reconstructive in nature and it is argued that this aspect of his performance challenges passive conceptions of semantic memory couched in terms of a catalogue of stored representations. It is proposed that the patient's disorder affects a dynamic, constructive, and inferential component of his knowledge base, and that this component is sensitive to semantic category.

Anomia↗